Tuesday, September 25, 2018

physical chemistry - What is the real pKa of water?


What is the $\text{p}K_\text{a}$ of water? A simple google search yields the value $15.74$, but this site and this paper say it's $14.0$.


According to my understanding, the correct answer should be $14.0$:


$$\text{p}K_{\text{a}}= -\log([\ce{H+}][\ce{OH-}])$$


For $25~\text{°C}$: $$[\ce{H+}][\ce{OH-}] = 10^{-14} = K_{\text{w}}$$


Thus follows $\text{p}K_{\text{a}}=14$.


Can you tell me which value is correct and why?





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